1. Field of the Invention
The present invention relates to zipper assemblies for reclosable packages which are large bags, particularly zipper assemblies which achieve high burst strengths, and the methods for manufacture thereof. These zipper assemblies may include sliders or may have a press-to-close configuration.
2. Description of the Prior Art
Large packages, bags or pouches, such as those used for pet food, charcoal, cat litter and similar items are typically filled and sealed shut, with no reclosure mechanism. These packages may be formed by form fill and seal (FFS) or by other methods. Prior attempts to incorporate a zipper reclosure mechanism have been unsatisfactory due to the unique requirements of a large bag with a relatively heavy load. In particular, filling from the bottom places all of the load on the reclosure during filling. This load can cause the zipper reclosure to fail and open. Similarly, dropping a filled bag onto a pallet or similar rough handling during transportation, as well as exposing a bag to elevated temperatures during transportation, can cause the zipper reclosure to fail.
The prior art has addressed these deficiencies by folding over the end of the package, particularly a multi-wall package, using an expensive label as tape thereby allowing successful filling and transport. Similarly, the prior art has addressed these deficiencies by using a liner peel seal below the zipper and a solid tear line in the zipper flange to provide a fill and transport system that does not rupture and spill the contents. However, these methods have slow rates of production, as well as increased costs of production, and frequently do not result in a satisfactory product for the consumer.
Some further examples of the prior art which are not entirely satisfactory are found in U.S. Pat. No. 6,979,482 entitled “Multiwall Bag with Zipper and Fin” issued on Dec. 27, 2005 to Hartzell et al. and U.S. Pat. No. 7,090,904 entitled “Enhanced Slider Zipper Multiwall Bag and Associated Methods” issued On Aug. 15, 2006 to Hartzell et al.
Typical prior tamper-evident zipper assemblies are disclosed in U.S. Pat. No. 6,354,738 entitled “Tamper Evident Reclosable Plastic Bag” issued on Mar. 12, 2002 to Buckman et al.; U.S. Pat. No. 4,647,063 entitled “Reclosable Bag with Laminated Liner and Method” issued on Jan. 13, 1987 to Sullivan; and U.S. Pat. No. 5,509,735 entitled “Closure Arrangement Having a Peelable Seal” issued on Apr. 23, 1996 to May.